Linux and the GNU System

Many computer users run a modified version of
the GNU system
every day, without realizing it. Through a peculiar turn of events,
the version of GNU which is widely used today is often called
“Linux”, and many of its users
are not aware
that it is basically the GNU system, developed by the
GNU Project.

There really is a Linux, and these people are using it, but it is just
a part of the system they use. Linux is the kernel: the program in
the system that allocates the machine's resources to the other
programs that you run. The kernel is an essential part of an
operating system, but useless by itself; it can only function in the
context of a complete operating system. Linux is normally used in
combination with the GNU operating system: the whole system is
basically GNU with Linux added, or GNU/Linux. All the so-called
“Linux” distributions are really distributions of
GNU/Linux.

Many users do not understand the difference between the kernel, which
is Linux, and the whole system, which they also call
“Linux”. The ambiguous use of the name doesn't help
people understand. These users often think that Linus Torvalds
developed the whole operating system in 1991, with a bit of help.

Programmers generally know that Linux is a kernel. But since they
have generally heard the whole system called “Linux” as well, they
often envisage a history that would justify naming the whole system
after the kernel. For example, many believe that once Linus Torvalds
finished writing Linux, the kernel, its users looked around for other
free software to go with it, and found that (for no particular reason)
most everything necessary to make a Unix-like system was already
available.

What they found was no accident—it was the not-quite-complete GNU
system. The available free
software added up to a complete system because the GNU Project
had been working since 1984 to make one. In
the The GNU Manifesto we set forth
the goal of developing a free Unix-like
system, called GNU. The
Initial Announcement of the GNU Project also outlines some of the
original plans for the GNU system. By the time Linux was started, GNU
was almost finished.

Most free software projects have the goal of developing a particular
program for a particular job. For example, Linus Torvalds set out to
write a Unix-like kernel (Linux); Donald Knuth set out to write a text
formatter (TeX); Bob Scheifler set out to develop a window system (the
X Window System). It's natural to measure the contribution of this
kind of project by specific programs that came from the project.

If we tried to measure the GNU Project's contribution in this way,
what would we conclude? One CD-ROM vendor found that in their “Linux
distribution”, GNU
software was the largest single contingent, around 28% of the
total source code, and this included some of the essential major
components without which there could be no system. Linux itself was
about 3%. (The proportions in 2008 are similar: in the “main”
repository of gNewSense, Linux is 1.5% and GNU packages are 15%.)
So if you were going to pick a name for the system based on
who wrote the programs in the system, the most appropriate single
choice would be “GNU”.

But that is not the deepest way to consider the question. The GNU
Project was not, is not, a project to develop specific software
packages. It was not a project to
develop a C compiler, although we did that. It was not a project
to develop a text editor, although we developed one. The GNU Project
set out to develop a complete free Unix-like system: GNU.

Many people have made major contributions to the free software in the
system, and they all deserve credit for their software. But the
reason it is an integrated system—and not just a
collection of useful programs—is because the GNU Project set out
to make it one. We made a list of the programs needed to make
a complete free system, and we systematically found, wrote,
or found people to write everything on the list. We wrote essential
but unexciting
(1) components because you can't have a system
without them. Some of our system components, the programming tools,
became popular on their own among programmers, but we wrote many
components that are not tools (2). We even
developed a chess game, GNU Chess, because a complete system needs
games too.

By the early 90s we had put together the whole system aside from the
kernel. We had also started a kernel, the
GNU Hurd, which runs on top of
Mach. Developing this kernel has been a lot harder than we expected;
the
GNU Hurd started working reliably in 2001, but it is a long way
from being ready for people to use in general.

Fortunately, we didn't have to wait for the Hurd, because of Linux.
Once Torvalds freed Linux in 1992, it fit into the last major gap in
the GNU system. People could
then
combine Linux with the GNU system to make a complete free system
— a version of the GNU system which also contained Linux. The
GNU/Linux system, in other words.

Making them work well together was not a trivial job. Some GNU
components(3) needed substantial change
to work with Linux. Integrating a complete system as a distribution
that would work “out of the box” was a big job, too. It
required addressing the issue of how to install and boot the
system—a problem we had not tackled, because we hadn't yet
reached that point. Thus, the people who developed the various system
distributions did a lot of essential work. But it was work that, in
the nature of things, was surely going to be done by someone.

The GNU Project supports GNU/Linux systems as well as the GNU
system. The FSF funded the rewriting of
the Linux-related extensions to the GNU C library, so that now they
are well integrated, and the newest GNU/Linux systems use the current
library release with no changes. The FSF also funded an early stage
of the development of Debian GNU/Linux.

Today there are many different variants of the GNU/Linux system (often
called “distros”). Most of them include non-free
software—their developers follow the philosophy associated with
Linux rather than that of GNU. But there are also
completely free GNU/Linux distros. The FSF
supports computer facilities
for gNewSense.

Making a free GNU/Linux distribution is not just a matter of
eliminating various non-free programs. Nowadays, the usual version of
Linux contains non-free programs too. These programs are intended to
be loaded into I/O devices when the system starts, and they are
included, as long series of numbers, in the "source code" of Linux.
Thus, maintaining free GNU/Linux distributions now entails maintaining
a free version of
Linux too.

Whether you use GNU/Linux or not, please don't confuse the public
by using the name “Linux” ambiguously. Linux is the
kernel, one of the essential major components of the system. The
system as a whole is basically the GNU system, with Linux added. When
you're talking about this combination, please call it
“GNU/Linux”.

Addendum: Aside from GNU, one other project has independently produced
a free Unix-like operating system. This system is known as BSD, and
it was developed at UC Berkeley. It was non-free in the 80s, but
became free in the early 90s. A free operating system that exists
today(4) is almost certainly either a
variant of the GNU system, or a kind of BSD system.

People sometimes ask whether BSD too is a version of GNU, like
GNU/Linux. The BSD developers were inspired to make their code free
software by the example of the GNU Project, and explicit appeals from
GNU activists helped persuade them, but the code had little overlap
with GNU. BSD systems today use some GNU programs, just as the GNU
system and its variants use some BSD programs; however, taken as
wholes, they are two different systems that evolved separately. The
BSD developers did not write a kernel and add it to the GNU system,
and a name like GNU/BSD would not fit the situation.(5)

Notes:

These unexciting but essential components
include the GNU assembler (GAS) and the linker (GLD), both
are now part of the GNU Binutils
package, GNU tar, and many more.

For instance, The Bourne Again SHell (BASH),
the PostScript interpreter
Ghostscript, and the
GNU C library are not
programming tools. Neither are GNUCash, GNOME, and GNU Chess.

Since that was written, a nearly-all-free
Windows-like system has been developed, but technically it is not at
all like GNU or Unix, so it doesn't really affect this issue. Most of
the kernel of Solaris has been made free, but if you wanted to make a
free system out of that, aside from replacing the missing parts of the
kernel, you would also need to put it into GNU or BSD.

On the other hand, in the years since this article
was written, the GNU C Library has been ported to several versions of
the BSD kernel, which made it straightforward to combine the GNU system
with that kernel. Just as with GNU/Linux, these are indeed variants of
GNU, and are therefore called, for instance, GNU/kFreeBSD and
GNU/kNetBSD depending on the kernel of the system. Ordinary users on
typical desktops can hardly distinguish between GNU/Linux and
GNU/*BSD.